1. Field of the Invention
The invention relates to a sheet feeding apparatus and an image forming apparatus, and particularly to a sheet feeding apparatus and an image forming apparatus having the retracting function of retracting a sheet containing member.
2. Description of the Related Art
Heretofore, in an image forming apparatus provided with a sheet feeding apparatus having a sheet containing member such as a sheet supplying cassette, sheets stacked on the sheet supplying cassette set at a predetermined mounting position in an apparatus main body have been successively supplied to an image forming portion, and image formation on the sheets has been effected in the image forming portion.
Now, the sheet supplying cassette which is the sheet containing member is detachably mounted with respect to the apparatus main body by a user's manual work for the purpose of filling up the container with sheets or changing the sheet size. At this time, there is a case where the sheet supplying cassette filled up with the sheets is not sufficiently pushed into the mounting position in the apparatus main body. In such a case, the sheet supplying cassette has not been positioned and as the result, an image has not been accurately formed on a sheet or the faulty conveyance of the sheet has occurred.
Also, particularly in a sheet feeding apparatus corresponding to A3 and LDR, the weight of the sheet feeding cassette plus the weight of sheets becomes 2N or greater, and the operability when the sheet supplying cassette is inserted into the mounting position becomes bad. So, heretofore, as described in Japanese Patent Application Laid-open No. 2004-117395, in order to improve the operability, there has been proposed a sheet feeding apparatus provided, for example, with a retracting device of a construction in which from this side of a regular mounting position in the sheet supplying cassette, the sheet supplying cassette is adapted to be forcibly retracted to the mounting position by the use of driving means such as a motor.
Also, as another retracting device, there is one in which a projected portion is provided on a sheet supplying cassette and also, a spring-biased rotary member is provided on an apparatus main body side, and when the projected portion gets over the rotary member, the rotary member is adapted to bias the projected portion by the resilient force of the spring. In this retracting device, as described in Japanese Patent Application Laid-open No. 2002-226065, design is made such that the sheet supplying cassette is biased through the projected portion, whereby the sheet supplying cassette is forcibly retracted from this side of the mounting position to the mounting position.
In such a conventional sheet feeding apparatus and a conventional image forming apparatus, however, in the case of a construction in which for example, the sheet feeding cassette is forcibly retracted to the mounting position by the use of driving means such as a motor, there is the problem that the construction becomes complicated and the apparatus becomes bulky and the cost also becomes high. Also, in the construction wherein the sheet supplying cassette is retracted by the spring-biased rotary member, there does not arise such a problem of the bulkiness and high cost of the apparatus. However, when the sheet supplying cassette is to be mounted, a separating member provided on the sheet supplying cassette for separating the sheets and a sheet feeding member provided in the apparatus main body frictionally contact with each other to provide the load of mounting or positioning resistance. Further, in a case where detecting means for detecting sheet sizes is provided on this side of the mounting position for the sheet supplying cassette, there is a load for the sheet size detection by this detecting means, and to overcome this load and perform the retracting operation, it is necessary to make the retracting force greater. That is, to reliably retract the sheet supplying cassette to the mounting position, it is necessary to use a spring of a great spring force. However, if use is made of such a spring of a great spring force, when the sheet supplying cassette is to be taken out of the apparatus main body, the cassette must be drawn out against the great spring force, and a great operating force becomes necessary, and this leads to the problem that operability is aggravated.